10 MHz is the usual frequency that test equipment uses for external reference. If I could get more than one cheap enough I could do some very interesting home physics experiments.

For example, does time pass differently inside a can at a million volts potential relative to ground? Both positive and negative rate measurements.

What about inside a large "A" field at the heart of a large toroid?

I suppose I could trim them to the same frequency before the experiments, but still $1000 for hone lab experiments is out of my price range.

(for me) Sometimes your job might make you run reference time for a large service provider... and then you need multiple reference signals... and then you realize you have spares that are going to be thrown away... and suddenly your home lab becomes way too geeky for you to admit to 99.999999989% of your friends... unless they also are on the same time email list as you ;)